Fractionation of mixtures of aromatic compounds utilizing gamma lactum solvents



"*t i "w and United States Patent FRACTIONATION F IVIIXTURES 0F AROMATIC COMPOUNDS UTILIZING GAMMA LACTUM SOLVENTS Glen C. Templeman, Findlay, Richard D. Morin, Co-

lnmbus, and Robert A. Ewing, Worthington, Ohio; said Morin and said Ewing assignors, by mesne assignments, to The Ohio Oil Company, Littleton, Colo., a corporation of Ohio No Drawing. Filed June 19, 1957, Ser. No. 666,770 18 Claims. (Cl. 260-674) wherein'the gamma-butyrolactam skeletal nucleus such as long-chain aliphatically substituted aromatic compounds, from aromatic compounds containing shorter chain aliphatic substituents and from unsubstituted aromatic hydrocarbons. v In copending application .Serial No. 566,393, filed February 20, 1956, there is disclosed a process for the selective fractionation of mixtures of aromatic hydrocarbons. The process disclosed and claimed therein is based upon the discovery that the solvent action of certaingammalactones can be selectively altered for certain aromatic hydrocarbons in preference to other aromatic hydrocarbons. The present invention is based upon the discovery that the capacity of certain gamma-lactams for aromatic hydrocarbons can be altered so as to selectively obtain different fractions of aromatic hydrocarbons from mixtures of, aromatic hydrocarbons. plished by the addition of controlled amounts, of water to the solution of the mixture of aromatic hydrocarbons in the gamma-lactam solvent. Unexpectedly, the fractions of aromatic hydrocarbons separated by the process of this invention are not equivalent to each other compositionwise. difier from each other in the proportions in which they initially existed in the aromatic hydrocarbon mixture. Thus, in the treatment of a mixture of aromatic hydrocarbons containing monoand polynuclear aromatic hydrocarbons, it is possible to obtain one or more fractions substantially enriched in the mononuclear aromaticconstituent of the mixture. Further, by the process of this invention, it is possible to obtain fractions substantially, enriched in the higher aliphatically substituted monoor polynuclear aromatic hydrocarbons from mixtures containing the same with other lesser aliphatically substituted corresponding aromatic hydrocarbons. The aliphatically substituted aromatic hydrocarbons are those which contain the greater number of carbon atoms in the aliphatic substituent in comparison with aliphatically substituted aromatic hydrocarbons which contain a lesser number of carbon atoms in the aliphatic substituent. Within the meaning of this definition, for example, mesitylene is a more highly aliphatically substituted mononuclear aromatic hydrocarbon than is benzene; triethylbenzene is a more highly aliphatically substituted aromatic hydrocarbon than is l-methylnaphthalene; and naphthalene is a lesser aliphatically substituted compound as compared to 2,6-dimethylnaphthalene. 7 v

The gamma-lactam solvents which are utilized to accomplish the'purpose of this invention are selected from the class of cyclic inner amides of gamma-amino acids.

The class of gamma-lactams suitable for. the purpose of this invention are the lactams of gamma-aminobutanoic The composition of the fractions separabler CE 7 Patented June 28,1960

acid and gamma-aminobutenoic acid and the alkyl-substituted lactams of these acids. .These gamma-lactams may be represented by the structural formula may be either saturated or unsaturated and wherein both I R and R may be either hydrogen or short-chain alkyl groups. It isto be understood that R, may represent more than one short-chain alkyl group attached to a substituttb; ble carbon atom in the gamma-butyrolactam skeletal nucleus. In general, the process is carried out by first obtaining a solution of the mixture of aromatic hydrocarbons in the chosen gamma-lactam solvent. For example, a mixture of benzene and aliphatically substituted benzene's maybe dissolved in the gamma-lactam. A controlled amount of Water preferably from about 10 to about 40-50 percent by volume of the solvent is added to the solution. The

' amountof Water added to the {solutionisan'amountsufiie cient to' spring some-of the hydrocarbons but insufiicient to spring all of the hydrocarbons from the gamma-lactam 35 solution." The water is intimately contacted with the gam:

This can be accomo separated from each other. The aromatics remaining pletely wash the remainder of the aromatics fromthe ma-lactam solution. Upon standing, there is separated an immiscible hydrocarbon fraction ,which is substantially enriched in. the higher aliphatically substituted benzenes. This fractionand the aqueous lactam phase are easily in the separated aqueous lactam phase may be recovered therefrom by the addition thereto of additional incremenatal additions of water to obtain further fractions ofthe:

' aromatic hydrocarbons, or in a sufiicient quantitytoc'omaqueous lactam phase. The lactam may be recovered for reuse by distillation of the .water from the residual aqueous lactam phase. Alternatively, the aromatics re-.

maining in the separated aqueous lactam phase may be 5o recovered therefrom by subjecting the phase to fractional detail. It should be understood that the specific embodi? ments contained in the examples are to be consideredas} illustrative of the invention and not in limitationthereoff In each of the examples aknown mixture of aromatic hydrocarbons was prepared and dissolved in the gammalactam solventi The composition of each of the hydro-- carbon fractions which separated upon each of the in-.

' cremental additions of water was determined by infrared analysis.

a Example I 5 A homogeneous solution composed of 25 parts of mesit:

ylene, 25 parts of benzene, and 150 parts of gamma-butyr-' olactam (Z-pyrrolidone), on a volume basis, was prepared. On the same volume basis, measured amounts of water were added to the solution until a first hydrocarbon fraction was sprung from the solution. The hydrocarbon fraction was separated, washed thoroughly with water, and I t then dried. This-same procedure was repeated. with addi tional incremental amounts of water as indicated in the table below.

Volume of Percent Composition Water by Volume Fraction No. (increments) Benzene Mesitylene 22 23. 2 76.8 3 22. 4 77. 6 3 23. 3 76. 7 3 26. 2 73. 8 23. 7 76. 3 g 26. 3 73.6 so "5; "f

Example 11 Percent Composition 7 Volume of by Volume Fraction No. Water- (incremonts) l-Methyl- Triethrl nan'hthnlpne benzene Example 111 A homogeneous solution consisting of parts of triethylbenzene, 10 parts of l-methylnaphthalene, and 80 parts of N-ethyl-gamma-butyrolactam (N-ethyl-pyrrolcapacity of the gamma-lactam solvents for difierent aromatic hydrocarbons: In general, the saturation point for the higher aliphatically substituted aromatic hydrocarbons has been found to be lowered to a greater degree with small amounts of waterthan the. saturation point for the lesser aliphatically substituted corresponding aromatic hydrocarbon. The amount of water suflicient to spring at least the first hydrocarbon fraction from the solution, of course, will vary with the particular gamma-lactam solvent and with the nature of the aromatic hydrocarbons dissolved therein, although an effective minimum amount of water appears to be about 10 percent by volume, based on the volume of the lactam solvent. When the total amount of the water added to the solution equals about 50 percent by volume of the solvent, there has then been a substantial change in the proportions of the aromatic hydrocarbon retained in the lactam solvent and this may be removed in the manner previously described. a

The above description and examples have been given for illustration of the invention and not for the purpose of limiting the invention specifically to the disclosure therein. Any modifications or variations of the invention as herein set forth may be made without departing from the spirit or scope thereof. Therefore, only such limitations should be imposed as are indicated in the claims.

What is claimed is:

1. The process of fractionating aromatic hydrocarbons from a mixture of a plurality of different aromatic hydrocarbons comprising (a) dissolving such a mixture of aromatic hydrocarbons in at least one gamma lactam selected from the group consisting of the lactams represented by the structural formula idone), on a volume basis, was prepared. On the same volume basis, measured amounts of water were incrementally added until a first hydrocarbon fraction was sprung from the solution. The hydrocarbon fraction was separated, washed thoroughly with water, and dried. The same procedure was used to collect additional hydrocarbon fractionswhich separated from the solution, as indicated in the following table.

Percent Composition Volume of by Volume Fraction No. Water (increments) l-Methyl- Triethyl naphthalene benzene Example IV A homogeneous solution consisting of .10 parts of naphthalene, 10 parts of 2,6-dimethylnaphthalene, both on a weight basis, and 200 parts by volume of gammabutyrolactam was prepared. On the same volume basis used for the lactam, 30 parts of water were added to the solution. The crystals which separated from the solution were filtered and washed thoroughly with'water and dried. The compositions of the crystals were determined by infrared' analysis to consist of 2.2 percent naphthalene and 94.5 percent of 2,6-dimethylnaphthalene, on a weight basis.

. The examples disclose that by the addition of various amounts of water it is possible to selectively alter the wherein R and R are selected from the class consisting of hydrogen and short-chain alkyl groups, (b) stepwise adding incremental amounts of water to the solution of the mixture of aromatic hydrocarbons in the gamma lactam to stepwise separate a series of fractions of aromatic hydrocarbons, and (c) removing each resultant immiscible fraction of aromatic hydrocarbons prior to the addition of the next subsequent incremental amount of water, so as to provide a series of fractions of aromatic hydrocarbons each having a composition different from the mixture from which it is separated.

2. A process according to claim 1 in which the lactam solvent is gamma-butyrolactam.

3. A process according to claim 1 in which the lactam solvent is gamma-N-methyl-butyrolactam.

4. The process of fractionating a mixture of aromatic hydrocarbons containing benzene and aliphatically substituted benzenes comprising (a) dissolving such a mixture of aromatic hydrocarbons in at least one gamma lactam selected from the group consisting of the lactams represented by the structural formula benzenes having a difierent composition from the mixtures from which it is separated.

5. The process of fractionating a mixture of aromatic hydrocarbons containing highly aliphatically substituted benzenes and lesser aliphatically substituted benzenes comprising (a) dissolving such a mixture of aromatic hydrocarbons in at least one gamma lactam selected from the group consisting of the lactams represented by the structural formula GR N \O wherein R and R are selected from the class consisting of hydrogen and short-chain alkyl groups, (b) stepwise adding incremental amounts of water to the solution of the mixture of aromatic hydrocarbons in the gamma lactam to stepwise separate a series of fractions of aromatic hydrocarbons, and (c) removing each resultant immiscible fraction of aromatic hydrocarbons prior to the addition of the next subsequent incremental amount of water, so as to separate therefrom immiscible aromatic hydrocarbons enriched in the highly aliphatically substituted benzenes each having a composition difierent from the mixture from which it is separated.

6. The process according to claim 5 wherein the lactam solvent is gamma-butyrolactam.

7. The process according to claim 5 wherein the lactam solvent is gamma-N-methyl-butyrolactam.

8. The process of fractionating a mixture of aromatic hydrocarbons containing highly aliphatically substituted mononuclear aromatic hydrocarbon and lesser aliphatically substituted polynuclear aromatic hydrocarbons comprising '(a) dissolving such a mixture of aromatic hydrocarbons in at least one gamma lactam selected from the group consisting of the lactams represented by the structural formula HR N o ill wherein R and R are selected from the class consisting of hydrogen and short-chain alkyl groups, (b) stepwise adding incremental amounts of water to the solution of the mixture of aromatic hydrocarbons in the gamma lactam to stepwise separate a series of fractions of aromatic hydrocarbons, and (c) removing each resultant immiscible fraction of aromatic hydrocarbons prior to the addition of the next subsequent incremental amount of water, so as to provide a series of immiscible hydrocarbon fractions enriched in the highly aliphatically substituted mononuclear aromatic hydrocarbons each hav:

ing a composition different from the mixture from which it is separated.

9. A process according to claim 8 wherein the substituted mononuclear aromatic hydrocarbons are substituted benzenes and the substituted polynuclear aromatic hydrocarbons are substituted naphthalenes and wherein the separated immiscible hydrocarbon fraction is enriched in highly aliphatically substituted benzenes.

10. The process according to claim 8 wherein one substituted mononuclear aromatic hydrocarbon is triethylbenzene and one substituted polynuclear aromatic hydrocarbon is l-methylnaphthalene.

11. The process of fractionating a mixture of aromatic hydrocarbons containing unsubstituted polynuclear aromatic hydrocarbons and aliphatically substituted polynuclear aromatic hydrocarbons comprising (a) dissolvwherein R and R are selected from the class consisting of hydrogen and short-chain alkyl groups, (b) stepwise adding incremental amounts of water to the solution of the mixture of aromatic hydrocarbons in the gamma lactam to stepwise separate a series of fractions of aromatic hydrocarbons, and (c) removing each resultant immiscible fraction of aromatic hydrocarbons prior to the addition of the next subsequent incremental. amount of water, so as to provide a series of fractions of aromatic hydrocarbons enriched in the aliphatically substituted polynuclear aromatic hydrocarbons each having a composition difierent from the mixture from which it is separated.

12. A process according to claim 11 in which the aliphatically substituted polynuclear aromatic hydrocarbons are methyl substituted derivatives thereof and the separated immiscible hydrocarbon fractions are enriched in methyl substituted polynuclear aromatic hydrocarbons,

13. A process according to claim 11 in which the substitued polynuclear aromatic hydrocarbons are naphthalenes. Y

14. The process according to claim 11 in which the 'lactam solvent is gamma-butyrola'ctam.

15. A process according to claim 11 wherein the lactam solvent is gamma-N-methyl-butyrolactam.

16. The process of fractionating a mixture of aromatic hydrocarbons containing unsubstituted monoand polynuclear hydrocarbons comprising (a) dissolving such-a mixture of aromatic hydrocarbons in atleast one gamma lactam selected from the group consisting of the lactams represented by the structural formula the addition of the next subsequent incremental amount of water, so as to provide a series of fractions of aromatic hydrocarbons enriched in the mononuclear aromatic hydrocarbons and each having a composition different I I from the'mixture from which it is separated.

17. A process according to claim 16 in which the lactam solvent is gamma-butyrolactam.

18. A process according to claim 16in which the lactam solvent is gamma-N-methyl-butyrolactam.

References Cited in the file of this patent UNITED STATES PATENTS 2,100,429 Bray Nov. 20, 1937 V p 2,737,538 Nelson Mar. 6, 1956' 2,771,494 Weedman Nov. 20, 1956 V 2,773,918 Stephens Dec. 11, 1956 2,812,372 Walsh et a1 Nov. 5, 1957 V 2,840,511

Rylander et al. June 24, 1958 

1. THE PROCESS OF FRACTIONATING AROMATIC HYDROCARBON FROM A MIXTURE OF A PLURALITY OF DIFFERENT AROMATIC HYDROCARBONS COMPRISING (A) DISSOLVING SUCH A MIXTURE OF AROMATIC HYDROCARBONS IN AT LEAST ONE GAMMA LACTAM SELECTED FROM THE GROUP CONSISTING OF THE LACTAMS REPRESENTED BY THE STRUCTURAL FORMULA 